When developing photos from Lightroom Classic to share in Instagram, it is important to remember Instagram aspect ratio and ideal post sizes. With this in mind, use any of the processes to develop photos based on your need:

For optimal image size and aspect ratio considerations, always crop and export from Lightroom first.

References

Andrew Aveley. (2021, September 21). Instagram photo size—How to crop for instagram in lightroom. https://www.youtube.com/watch?v=myZ4kC15VlU

Dunna Did It. (2019, February 25). How To Split Pictures For Instagram // Seamless Multi-Post Tutorial. https://www.youtube.com/watch?v=cgKcF8mw2Z4